Hand-held and other electronic devices have become an intrinsic part of everyday life. In addition to the convenient services they provide, their sleek, modern appearance is essential to their marketability. Shapes, colors, and surfaces are optimized to maximize consumer appeal. Some housing and display surfaces are high gloss while others are matte finish, with combinations providing particular aesthetic appeal.
Transparent screens such as display screens and touch screens appear more and more frequently on interactive electronic devices. Reducing glare of the screens is desired to maximize visibility of the displays in different lighting environments. There are various known methods of reducing the glare of transparent substrate surfaces. An exemplary method involves depositing a light interference coating stack on the substrate that reduces reflection by exploiting the optical interference within adjacent thin films. Such films usually have a thickness of about one-quarter or one-half the nominal wavelength of visible light, depending on the relative indices of refraction of the coatings and substrate. Another method includes forming a light scattering means at the surface of the substrate, such as by mechanically altering the outermost surface of the substrate or through use of a diffuser coating on the glass substrate.
Interference coatings reduce glare without reducing resolution. However, they are relatively expensive to deposit, requiring the use of vacuum deposition techniques such as sputtering and precise manufacturing conditions, or very precise alkoxide solution dip coating techniques, with subsequent drying and firing steps. Strict processing parameters must be observed to obtain the desired results.
Fillers are widely used in the coatings industry to affect gloss and they are known to provide glare resistance to both transparent and opaque (such as metal) substrates in many cases. Fillers control gloss by affecting the surface roughness of an applied coating.
Etching the outer surface of the substrate or otherwise chemically or mechanically modifying the outer surface of a coating deposited on the substrate has been attempted in an effort to reduce glare by diffusion of light. There are numerous drawbacks to such modification techniques. Etching by chemical means involves handling and storage of generally highly corrosive compounds (e.g. hydrofluoric acid). Such compounds create processing and disposal problems in view of increasingly stringent environmental laws. Etching by non-chemical means, such as by sandblasting, necessitates additional and costly processing operations.
It would be desirable to provide an alternative method of forming an anti-glare coating on a substrate while avoiding the drawbacks of the prior art.